Manually operated trigger switch for rotatable electric tools



June 23, 1964 MANUALLY OPERATED TR R. E. LARKIN 3,138,689

IGGER SWITCH FOR ROTATABLE ELECTRIC TOOLS Filed NOV. 2, 1959 3Sheets-Sheet l J n 23, 9 4 R. E. LARKlN 3,138,689

MANUALLY OPERATED TRIGGER SWITCH FOR ROTATABLE ELECTRIC TOOLS Filed Nov.2, 1959 3 Sheets-Sheet 2 8 24 Ma 39a Zea June 23, 1964 R. E. LARKlN3,138,689

MANUALLY OPERATED TRIGGER SWITCH FOR ROTATABLE ELECTRIC TOOLS Filed Nov.2, 1959 3 Sheets-Sheet 3 United States Patent 3,138,639 MANUALLYOPERATED TRIGGER SWITCH FOR RGTATABLE ELECTRIC TOOLS Robert E. Larkin,Milwaukee, Wis, assignor to Cutler,

Hammer, Inc, Milwaukee, Wis., a corporation of Delaware Filed Nov. 2,i959, Ser. No. 850,225 4 Claims. (Cl. 260-168) This invention relatesgenerally to electric switches. More particularly, the invention relatesto manually operated trigger type switches which are adapted for use inportable electric tools, but the invention is not limited thereto.

It is an object of the invention to provide improved switches of theaforesaid character which are readily interchangeable with present typesof trigger switches.

Another and more specific object is to provide improved manuallyoperated, normally olf-momentary on, slow-make and slow-break, singlepole, single throw, in-line motion trigger switches which are especiallyadapted for use in portable electric tools.

Still another object is to provide improved switches of the aforesaidcharacter which are characterized by improvements in the means ofassembly, namely a snap together feature.

A further object is to provide improved switches of the aforesaidcharacter which are compact, employ a minimum number of parts, arerelatively simple in structure and mode of operation, lend themselvesreadily to mass production techniques, and are reliable in operation.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate preferred embodiments of theinvention which will hereinafter be described, it being understood thatthe embodiments shown are susceptible of modification with respect tocertain details thereof without departing from the scope of the appendedclaims.

In the drawings:

FIGURE 1 is a side elevational view of a trigger switch incorporatingthe invention shown mounted within the pistol grip handle of a portableelectrical tool;

FIG. 2 is an elevational view of the rear end of the handle-mountedswitch shown in FIG. 1;

FIG. 3 is a top plan view of the switch showing portions of its lockingmechanism in cross-section;

FIG. 4 is a bottom plan view of the switch;

FIG. 5 is a cross-sectional view of the switch showing it in normallyolf position; the upper portion of the cross section being taken alongline 5a-5a of FIG. 3 and the lower portion of the cross-section beingtaken along line 5b5b of FIG. 7;

FIG. 6 is a cross-sectional View of the switch taken along line 6-6 ofFIG. 5;

FIG. 7 is a top plan view showing the interior of the base of the switchand the stationary contacts and a bussing connector therewithin;

FIG. 8 is a side elevational view of the switch frame;

FIG. 9 is an isometric view of the bussing connector which is shownremoved from the switch base;

FIG. 10 is a bottom plan view of the trigger member of the switch;

FIG. 11 is an enlarged isometric view of the base of the switch withportions cut away to expose structural details therewithin;

FIGS. 12, 13 and 14 are enlarged cross-sectional views, similar to theview in FIG. 6 showing various stages of the connection of the switchframe to the switch base during assembly; and

FIG. 15 is a cross-sectional view of a portion of the trigger of theswitch, similar to the view in FIG. 5, showing an alternative form ofconstruction.

It will be understood that in the various figures similar elements aredesignated by the same reference numerals.

Referring FIGS. 1, 2 and 3, the numeral 20 designates a trigger switchincorporating the invention which is shown mounted in the pistol griphandle 21 of a portable electric tool which, for example, may be assumedto be provided with a motor (not shown). Handle 21, which preferably isformed of cast aluminum, is separable into two sections and is providedwith integrally formed projections 21a on the opposite inside wallsthereof which entrap switch 20 and with an aperture 21b through whichthe trigger 23 of the switch extends. Handle 21 is also provided with ahole 21c in the side wall thereof through which the lock button 46 ofthe switch 20 extends and with a hole 21d in the bottom wall thereofthrough which the insulated power supply leads L1 and L2 extend. Supplylines L1 and L2, which may be assumed to be connected to a suitablesource of A.-C. power supply (not shown), extend into switch 20, and twoinsulated wire leads M1 and M2, which may be assumed to be connected tothe tool motor (not shown), also extend into the switch. As willhereinafter appear, leads L2 and M2 are electrically connected to eachother through a bussing connector within switch 20 and leads L1 and M1are connected to individual stationary contacts within the base, whichcontacts are adapted to be bridged to complete an energizing circuit forthe tool motor (not shown) when the trigger 23 of the switch isdepressed.

Referring generally to FIGS. 1 through 10, switch 20 comprises a basemember 22 and a trigger member 23 which is slidably movable with respectto the base. Preferably, base 22 and trigger 23 are molded fromelectrical insulating material such as Bakelite or the like. Trigger 23is associated with base 22 by a rigid frame member 24, preferably formedby stamping from sheet metal, which is rigidly secured to the base, aswill hereinafter be explained.

As FIGS. 4 through 7 show, base 22 rigidly supports the twospaced-apart, electrically conductive, stationary contact members 25 and26 which are adapted to have leads M1 and L1 (shown in FIGS. 1 and 2),respectively, electrically and mechanically connected thereto as bysoldering or other suitable means. Base 22 also rigidly supports theelectrically conductive, bussing connector 27, best seen in FIG. 9,which is not electrically connected to any portion of switch 20, butwhich is adapted to have the leads M2 and L2 electrically andmechanically connected thereto as by soldering or other suitable meansas a convenient means for electrically connecting those leads together.Stationary contacts 25 and 26 and bussing connector 27 are preferablyformed by stamping from sheet bronze or similar material. Since contacts25 and 26 are substantially identical in configuration and manner ofattachment to base 22 of switch 20, although they are reversely disposedtherein, only contact 26 will be described in detail hereinafter.

As FIGS. 4 through 7 and 11 show, base 22 is molded so that the flatupper surface 28 thereof is provided with a shallow substantiallyrectangular recess 29 in the bottom of which is a deeper, substantiallyU-shaped recess 30, the legs of which recess 30 communicate by means ofthe slots 31 and 32, respectively, with the cavities 33 and 34,respectively, in the bottom of the base. The right-hand end ofrectangular recess 29 communicates by means of a slot 35 with a cavity36 in the bottom of the base.

As FIGS. 5, 6 and 7 show, stationary contact 26 initially is asubstantially flat member bent over and cambered at the top thereof toprovide a contact surface 26a. The bent over portion of contact 26 restson a projection 32a which is integral with the wall and the floor of theleg of the U- shaped recess 30 in base 22 as FIGS. 6, 7 and 11 show. Themiddle portion of contact 26 fits snugly within slot 32 in base 22 andthe tang of the contact which is provided with a wire attachment hole26b, depends into cavity 34. Contact 26 is secured to base 22 by stakingor outwardly shearing the two tabs 26c after the contact is in place inthe base.

As FIGS. 4, 5, 6, 7 and 9 show, bussing connector 27 initially is asubstantially U-shaped member having a struck out tongue 27a whichengages the top wall of cavity 36. After the connector 27 is in place inthe base 22 the top projection 27b thereof is bent over, as FIGS. and 7show, to rigidly secure the connector to the base.

As FIG. 11 shows, base 22 is adapted to have frame 24 rigidly securedthereto and for this purpose is provided with two elongated slots 38 and39 which extend from the upper surface 28 thereof and communicate withthe cavities 33 and 34, respectively, formed in the bottom of the base.The walls of the slots 38 and 39 are substantially perpendicular but theoutermost walls therein are provided with integrally formed projections38a and 39a, respectively.

Each projection 38a and 3911, which extends only part of the length ofits slot so that space exists at either end thereof preferably has atriangular cross-sectional configuration. Thus, the surface thereofslopes downwardly and away from the wall of the slot from which itprojects. The bottom surface of each projection is substantially fiatand projects at a right angle from the wall of the slot.

As FIGS. 1 through 6 and 8 show, frame 24 is rigidly secured to base 22and maintains trigger 23 in proper relationship therewith. Frame 24comprises a top wall 24a having two indexing holes 2411 and 24i, tworectangular cutouts 24g therein, an end wall 241), and tWo side wallsfrom which the ears 24c and 24d, respectively, depend. The ears 24c and24d are provided with the apertures 24a and 24 respectively, which areadapted to engage the projection 39a and 38a, respectively, in the slotsin base 22. As FIGS. 12, 13 and 14 show, frame 24 fits over trigger 23and is pressed down so that the ears enter the slots and graduallyconverge as they slide down the surfaces of the projection. Convergenceis possible since the ears are resilient and there is clearance withinthe slots. When the apertures in the ears register with the projections,the resiliency of the sides of the frame cause the ears to spring backto their normal position and the apertures in the ears engage theprojections thereby causing the frame to be secured to the base. It isto be understood that trigger 22, which fits snugly within frame 24,prevents inward springing of the sides and ears of the frame todisengage the ear apertures from the projection and the interlockedassembly cannot be disassembled without damaging the device. Anotheradvantage of this means of assembly is that no tools or fasteningdevices are needed to secure the frame to the base.

As FIGS. 1 through 6 and show, trigger 23 has a portion which is adaptedto be gripped by the operators finger and an elongated portion whichextends back therefrom which is adapted to be entrapped by frame 24. Thefiat bottom surface 23a of trigger 23 is provided with two integrallyformed, parallel guide ribs 23b which extend into shallow recess 29 ofbase 22 and slide along the inside side walls thereof to aline and guidethe trigger as it moves. The top surface of trigger 23 is provided withtwo integrally formed projections 230 which are adapted to extendthrough the cutouts 24g in the top wall 24a of frame 24 and cooperatetherewith to limit forward and rearward travel of the trigger withrespect to the frame and base. Trigger 23 is further provided with ahorizontally disposed groove 23d, open at one end, which accommodates ahelically shaped compression spring or return spring 40 which bearsagainst the end of the groove and end wall 24b of frame 24 and tends tobias the trigger outwardly of the frame to off position.

As FIGS. 5 and 10 show, the bottom of trigger 23 is provided with acontact cavity 23c which is adapted to accommodate a bridging contactmember 41, best seen in FIGS. 5 and 6, which is a substantially U-shapedstrip of electrically conductive material such as bronze. An aperture 23extends from contact cavity 23a through the upper portion of trigger 23and accommodates a ball detent 42, formed of relatively hard,electrically nonconductive material such as glass, and a helicallyshaped compression spring or contact loading spring 43 which bearsupwardly against ball detent 42 and downwardly against bridging contact41. It will be understood that ball-detent 42 cooperates with the indexholes 2411 and 24i to indicate to the operator by feel the properlocation of the trigger 23 and bridging contact 41 with respect to thebase 22 and the stationary contacts and 26. The fact that the balldetent 42 is fabricated of insulating material prevents an electricalcircuit from existing between bridging contact 41, spring 43, the balldetent, and metal frame 24 which might endanger the operator.

Normally, upon release of finger pressure, trigger 23 is biased to offposition by return spring and the various members of the switch assumethe position hereinbefore described.

Normally, as FIGS. 1, 2, 3, 4, 5 and 6 show, trigger switch 20 is in offcondition. That is to say, return spring 40 biases trigger 23 outwardlyof frame 24 and ball detent 42 is biased into forward indexing hole 2411by contact loading spring 43. Spring 43 also biases bridging contact 41against the floor of shallow recess 29 in base 22.

FIG. 15 shows an alternative form of switch construction wherein theball detent is omitted. In the alternative form of construction the topwall 24a of the frame need not be provided with indexing holes andtrigger 23 is .not provided with a hole, comparable to hole 23 in thefirst embodiment of the switch, which extends completely through thetrigger. In all other respects, however, the embodiment shown in FIG. 15operates in the same manner as the first embodiment, except that thefeel indication is absent.

FIGS. 1, 2, 3, 4 and 6 show that switch 20 is provided with means forlocking the switch in on or closed condition. As FIGS. 3 and 8 show, theside wall of frame 24 is provided with a circular hole 24j whose edgeflares outwardly. A substantially cylindrical pin 34, which has amushroom-like head which is of greater diameter than circular hole 24extends through hole 24 and the serrated end of the pin is force-fittedin a hole provided in a pushbutton 46 which is preferably formed ofelectrical insulating material. A compression spring 47, which surroundspin 45 and is disposed between the side wall of frame 24 and pushbutton46, normally biases the pushbutton and the pin outwardly of the frame sothat the head of the pin fits snugly within the depression formed by theflared edge of circular hole 24j. When the trigger switch 20 is disposedwithin tool handle 21, pushbutton 46 extends through the hole 21c in thehandle and is afforded support by the handle. The side of trigger 23 ofthe switch 20 is provided with a depression 23h, best seen in FIG. 3,which atfords clearance for the head of pin 45. When the trigger 23 isdepressed, pushbutton 46 may be depressed and the pin 45 will extendthrough a cut-away portion 23i in the wall of the trigger and the headof the pin will interfere with the edge of the wall to prevent outwardmovement of the trigger even after finger pressure on the trigger isreleased. To release the lock, trigger 23 is depressed slightly to takethe strain off pin 45 and spring 47 causes the pin to bias outwardly toits normal position clear of the trigger. Then, upon release of fingerpressure, trigger 23 is free to return to its normal off position. It isto be noted that a rigid sleeve which ordinarily would be attached toframe 24 to afford support for the pushbutton 45, pin and spring is notneeded in the type of device described herein since the pushbutton issupported directly by the tool handle.

The switch 20 operates as follows: Assume that the switch is mountedwithin tool handle 21, is shown in FIGS. 1, 2 and 3, and that theenergized supply conductors L1 and L2 are connected to stationarycontact 26 and to buss 27, respectively and that the motor leads M1 andM2 are connected to stationary contact 25 and to buss 27 respectively.

Normally, the return spring 40 biases trigger 23 to the off position, asshown in FIGS. 1, 2, 3, 4, 5 and 6, i.e., so that trigger is movedoutwardly of frame 24 as far as is permitted by the cooperation ofprojection 23c of the trigger with the slots 24g of frame 24. In thisextreme position the spring 43, which is under compression, acts uponbridging contact 41 to bias it against the floor of shallow recess 29 inbase 22 and acts upon ball detent 42 to bias it into forward indexinghole 24h in the top wall 24a of frame 24. In this condition, of course,no electrical contact is established between the stationary contacts.

To effect closure of switch 20, the trigger 23 is pushed inwardly offrame 24 against the bias of return spring 40. Initially, as pressure isapplied to trigger 23, ball detent 42 is forced to disengage forwardindex hole 24h of frame 24 and rides against the under surface of thetop wall 24a of the frame. Simultaneously, trigger 23 slides bridgingcontact 41 across the floor of shallow recess 29 in base 22 and overonto the cambered surfaces of stationary contacts 25 and 26 in base 20where it is held in good contact by the pressure of spring 43. Rearwardtravel of trigger 23 is limited by the projection 23c thereof whichcooperates with the slots 24;; of frame 24. In rearward position, whenbridging contact 41 is in proper position with respect to the stationarycontact, the ball detent 42 registers with rear indexing hole 24i in topwall 24a of frame 24. As trigger 23 is moved rearwardly return spring 40is compressed, thereby loading it to effect return of the trigger whenfinger pressure on the trigger is released.

Upon release of pressure, return spring 40 effects return of trigger 23to the normal or off position hereinbefore described.

It is apparent that in the embodiments of the invention disclosed hereinthe frame 24 attaches movable trigger 23 to base 22 by means of a pairof depending legs which are inserted into separate slots in the base. Itis to be understood that a single cavity in a base member havingoppositely disposed projections on opposite walls could be employed.Furthermore, the member or element which is attached to a base by aframe need not necessarily be movable as is the trigger 23. It shouldalso be noted that a frame member having only a single depending portionadapted to engage a projection in a slot would serve to attach the frameto a base provided, of course, that some other portion of the frame suchas the other side thereof, was rigidly anchored to the base in asuitable manner.

I claim:

1. In an electric switch, in combination, a base, at least onestationary contact supported by said base, spacedapart slots extendinginto said base from a surface thereof, a projection extending from theoutermost Wall of each slot, a movable member slidably positioned onsaid surface of said base, said movable member having a movable contactcooperating with said stationary contact, and a frame entrapping saidmovable member to maintam said member slidably positioned with respectto said surface of said base, said frame having resilient portions whichextend beyond the surface of said member which is in association withthe said surface of said base, each resilient portion being providedwith an aperture which is adapted to engage the projection in the cavityinto which said resilient portion is inserted to attach said frame tosaid base.

2. In an electric switch, in combination, a molded insulating base, apair of spaced-apart contacts supported by said base, slots within saidbase, a member slidable on said base and having a contact which is movedthereby into and out of bridging engagement with said spacedapartcontacts, and a frame having a portion holding said member on said base,said frame also having apertured portions which when inserted into saidslots within said molded insulating base spring into self-lockingengagement about projections formed on said base within said slots tohold said member in confined slidable operating relation on said base.

3. In an electric switch, in combination, an insulating base, a pair ofstationary contacts supported by said base, slots within said base, atrigger member slidable on said base, a bridging contact slidablymovable with said trigger member, a frame having a portion straddlingsaid trigger member, said frame also being provided with resilientdepending portions which are adapted to extend into said slots withinsaid base to lockingly engage said frame and said base, a springdisposed at one end against said frame and at its other end against saidtrigger to bias said trigger into given position, a loading springdisposed between said bridging contact, and an insulated indexing membermovable with said trigger member and adapted to cooperate with indexingholes in said frame, said loading spring adapted to bias said bridgingcontact into engagement with said stationary contacts and to bias saidindexing member into respective indexing holes in said frame.

4. The combination according to claim 3 including a spring disposeddirectly between said bridging contact and said trigger member to biassaid bridging contact into engagement with said stationary contacts whensaid trigger member is moved from said given position.

References Cited in the file of this patent UNITED STATES PATENTS2,502,600 Spender Apr. 4, 1950 2,618,723 Mahaffay Nov. 18, 19522,665,353 Popp Jan. 5, 1954 2,744,176 Kaman May 1, 1956 2,789,170Johnson Apr. 16, 1957 2,881,292 Winter et a1. Apr. 7, 1959 2,922,012OMara Jan. 19, 1960 2,928,921 Cranmose Mar. 15, 1960 2,936,349 JohnsonMay 10, 1960

2. IN AN ELECTRIC SWITCH, IN COMBINATION, A MOLDED INSULATING BASE, APAIR OF SPACED-APART CONTACTS SUPPORTED BY SAID BASE, SLOTS WITHIN SAIDBASE, A MEMBER SLIDABLE ON SAID BASE AND HAVING A CONTACT WHICH IS MOVEDTHEREBY INTO AND OUT OF BRIDGING ENGAGEMENT WITH SAID SPACEDAPARTCONTACTS, AND A FRAME HAVING A PORTION HOLDING SAID MEMBER ON SAID BASE,SAID FRAME ALSO HAVING APERTURED PORTIONS WHICH WHEN INSERTED INTO SAIDSLOTS WITHIN SAID MOLDED INSULATING BASE SPRING INTO SELF-LOCKINGENGAGEMENT ABOUT PROJECTIONS FORMED ON SAID BASE WITHIN SAID SLOTS TOHOLD SAID MEMBER IN CONFINED SLIDABLE OPERATING RELATION ON SAID BASE.